Product Development of the Vaccine
The studies described above provide a strong preclinical foundation for accelerating the development of a therapeutic human vaccine for Chagas disease. The authors are currently working to produce a vaccine for initial clinical testing in Mexico and elsewhere in Latin America where Chagas disease is highly endemic. To actually produce a vaccine under current good manufacturing practices (cGMP) suitable for Phase I clinical testing requires the implementation of a number of key steps, including:
The development of a process for the high-yield and low-cost expression, fermentation and purification of the two component recombinant antigens of the Chagas disease vaccine – that is, Tc24 and TSA-1 – followed by formulation on alum (Alhydrogel® [Brenntag Biosector, Frederikssund, Denmark] or aluminum phosphate) together with E6020, a synthetic TLR4 agonist;
The development and qualification of product-specific assays (including potency assays), followed by the process and formulation optimization, which incorporates biophysical profiling;
Technology transfer for the cGMP manufacture of both drug substance and drug product;
Formal release of the drug product based upon qualified assays and a formal stability program, which includes vaccine potency;
A preinvestigational new drug meeting followed by completion of a good laboratory practice (GLP) toxicology study;
Investigational New Drug (IND) submission to begin clinical testing.
The major deliverable at the end of the project period is the concurrence of the US (FDA) and Mexican (COFEPRIS) national regulatory authorities with plans for initial Phase I clinical testing of the Chagas disease vaccine in Mexico, followed by further clinical testing throughout other areas of Latin America. Thus, the authors are advancing the development of two candidate antigens for the first vaccine against Chagas disease. The Carlos Slim Institute for Health (Instituto Carlos Slim de la Salud; Mexico City, Mexico), together with the Southwest Electronic Energy Medical Research Institute and Texas Children's Hospital (TX, USA), has made an initial commitment to fund early development of the two T. cruzi vaccine candidate antigens. The vaccine development initiative is led by the nonprofit Sabin Vaccine Institute (DC, USA) Product Development Partnership (PDP), an internationally recognized PDP and one of the only PDPs with a specific mission to develop and test new vaccines to combat the neglected tropical diseases.[59] PDPs are nonprofit organizations that use industry practices to advance new neglected disease products, such as small-molecule drugs, vaccines, diagnostics, microbiocides and insecticides.[59] Worldwide there are approximately 16 PDPs including five committed to vaccine development. The Sabin Vaccine Institute PDP has built the infrastructure and capacity for research, development and scale-up technology transfer for potential vaccine candidates, especially to developing country manufacturers in Brazil (i.e., FIOCRUZ BioManguinhos [Rio de Janeiro, Brazil] and Instituto Butantan [Sao Paulo, Brazil]) and Mexico (see below), as well as a strong management and administrative core experienced in vaccine development, quality assurance, regulatory affairs and clinical trials. Sabin Vaccine Institute's 11 years of research and development experience has generated a comprehensive, low-cost model that serves as a blueprint for vaccine development and ongoing efforts to fight public health threats that adversely impact more than 1 billion people worldwide. Such activities include new vaccines for hookworm infection and schistosomiasis, which have either entered or will soon enter clinical testing.[59] The partnership for accelerating the first therapeutic Chagas vaccine for human trials is illustrated in Figure 2 and summarized in Box 3. Briefly:
Figure 2.
Partnership for the development of a human therapeutic Chagas disease vaccine.
cGMP: Current good manufacturing practice; GLP: Good laboratory practice; PDP: Product development partnership.
Sabin Vaccine Institute PDP, in collaboration with its affiliated Texas Children's Hospital Center for Vaccine Development, will express the recombinant antigens (10–20 l fermentation scale for yeast, bacteria and other expression systems, together with downstream purification) and perform process development and technology transfer activities for manufacture in collaboration with Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV), the center for research and advanced studies in Mexico City (Mexico).[101] Sabin will also provide regulatory affairs and quality assurance support. A hallmark of this activity is that the Sabin Vaccine Institute PDP selects processes – that is, microfiltration, ultrafiltration, centrifugation, column resins and assays – which are compatible with the pilot manufacturing facility of the GMP manufacturer at the 60–100 l scales. Upon execution of a manufacturing agreement for the production of Phase I clinical trial material, a productive research clone will be provided to the cGMP manufacturer for the generation of master/production cell banks;
UADY will evaluate the antigenicity, immunogenicity and preclinical efficacy of the Chagas vaccine candidates;
Birmex (Laboratorios de Biológicos y Reactivos de México – Mexico's leading and public sector vaccine manufacturer) will perform cGMP manufacture. Birmex is a Mexican state-owned institution under the supervision of the Federal Secretary of Health, and is dedicated to research, development and production of venoms, different anti-venom purified polyclonal immunoglobulins and vaccines.[102] Birmex currently produces a number of vaccines for Mexico;
The partnership has obtained the access for the testing and evaluation of a novel adjuvant through the commitment from the Japanese company Eisai Co., Ltd, which has pioneered the development of the synthetic TLR4 agonist, E6020, as a vaccine adjuvant;[45]
Additional partners include the Bernhard Nocht Institute for Tropical Medicine (BNI; Hamburg, Germany), which has extensive experience in the immunology of Chagas disease,[60–62] University of Kansas (KS, USA) for biophysical and formulation assessments,[63] and the PHICOR group of the University of Pittsburgh School of Medicine and Graduate School of Public Health (PA, USA).[3]
Based on our previous success with technology transfer, the authors expect that the production processes will yield Tc24 and TSA-1 drug substance and drug products of sufficient yield, purity and stability for use in Phase I testing. Following GLP toxicology testing, a regulatory filing for each of the candidate antigens will be prepared and submitted both to the US FDA and the Mexican national regulatory authority (COFEPRIS) (Box 4).
For quality control and assurance, an extensive array of assays has been developed and implemented for protein characterization. These assays are employed in the earliest stages of the candidate antigen and are refined for the specific antigen concurrently with the early process development. The Sabin Vaccine Institute PDP and Texas Children's Center for Vaccine Development performs assay qualifications to establish that assays used for the recombinant vaccine antigen characterization are accurate, precise, sensitive, specific, reproducible and robust. Based on these qualification procedures, a set of release specifications will be established to support the regulatory submission to the FDA and COFEPRIS for the recombinant antigen vaccine. All assays use standard published procedures or modified procedures established by the Sabin Vaccine Institute PDP as a part of its hookworm vaccine development program and will be codeveloped with Birmex/CINVESTAV to assure smooth technology transfer and product release. These assays will establish criteria for the evaluation of the expression during 'scale-up' and 'final lock-down' as well as for the stability program of the recombinant proteins. Most of these assays are antigen-specific and will be developed through application and/or modification of methods currently existing in our laboratories. In addition, a variety of assays have been developed, maintained and qualified in order to analyze pH, protein concentration determination by UV absorbance and endotoxin content. All assays will complement biophysical methods for the generation of protein conformational maps or diagrams. This approach will provide confirmation of a successful, consistent and reproducible process development strategy.
Expert Rev Vaccines. 2012;11(9):1043-1055. © 2012 Expert Reviews Ltd.
